Liquid crystal composition and liquid crystal display device

ABSTRACT

The subject is to provide a liquid crystal composition that satisfies at least one of characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of a nematic phase, a small viscosity, a suitable optical anisotropy, a negatively large dielectric anisotropy, a large specific resistance and a high stability to ultraviolet light or heat, or that is suitably balanced regarding at least two of the characteristics. The subject is to provide a AM device that has a short response time, a large voltage holding ratio, a large contrast ratio, a long service life and so forth. The invention provides a liquid crystal composition that has negative dielectric anisotropy, including a specific four-ring compound having a high maximum temperature and a negatively large dielectric anisotropy as a first component, a two-ring compound having a small viscosity as a second component, and optionally including a specific compound having a negatively large dielectric anisotropy as a third component, a specific compound having small viscosity as a fourth component and a specific compound having a negatively large dielectric anisotropy as a fifth component. The invention provides also a liquid crystal display device containing this composition.

This nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2010-006537 filed in Japan on Jan. 15, 2010,the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates mainly to a liquid crystal composition suitablefor use in an active matrix (AM) device, and an AM device containing thecomposition. More specifically, the invention relates to a liquidcrystal composition having negative dielectric anisotropy, and a devicecontaining the composition and having a mode such as in-plane switching,vertical alignment or polymer sustained alignment.

2. Related Art

In a liquid crystal display device, a classification based on anoperating mode for liquid crystals includes phase change (PC), twistednematic (TN), super twisted nematic (STN), electrically controlledbirefringence (ECB), optically compensated bend (OCB), in-planeswitching (IPS), vertical alignment (VA) and polymer sustained alignment(PSA). A classification based on a driving mode in the device includes apassive matrix (PM) and an active matrix (AM). The PM is furtherclassified into static, multiplex and so forth, and the AM is classifiedinto a thin film transistor (TFT), a metal-insulator-metal (MIM) and soforth. The TFT is further classified into amorphous silicon andpolycrystal silicon. The latter is classified into a high temperaturetype and a low temperature type according to the production process. Aclassification based on a light source includes a reflection typeutilizing natural light, a transmission type utilizing a backlight and asemi-transmission type utilizing both natural light and a backlight.

These devices contain a liquid crystal composition having suitablecharacteristics. The liquid crystal composition has a nematic phase.General characteristics of the composition should be improved to give anAM device having good general characteristics. Table 1 below summarizesthe relationship between the general characteristics of the two. Thegeneral characteristics of the composition will be explained furtherbased on a commercially available AM device. The temperature range of anematic phase relates to the temperature range in which the device canbe used. A desirable maximum temperature of the nematic phase isapproximately 70° C. or higher and a desirable minimum temperature ofthe nematic phase is approximately −10° C. or lower. The viscosity ofthe composition relates to the response time of the device. A shortresponse time is desirable for displaying moving images on the device.Accordingly, a small viscosity of the composition is desirable. A smallviscosity at a low temperature is more desirable.

TABLE 1 General Characteristics of Composition and AM Device GeneralCharacteristics No. General Characteristics of Composition of AM Device1 wide temperature range of a nematic phase wide usable temperaturerange 2 small viscosity¹⁾ short response time 3 suitable opticalanisotropy large contrast ratio 4 positively or negatively largedielectric low threshold voltage anisotropy and small electric powerconsumption large contrast ratio 5 large specific resistance largevoltage holding ratio and large contrast ratio 6 high stability toultraviolet light and heat long service life ¹⁾A liquid crystalcomposition can be injected into a liquid crystal cell in a shorterperiod of time.

The optical anisotropy of the composition relates to the contrast ratioof the device. The product (Δn×d) of the optical anisotropy (Δn) of thecomposition and the cell gap (d) of the device is designed so as tomaximize the contrast ratio. A suitable value of the product depends onthe kind of operating modes. In a device having a VA mode, a suitablevalue is in the range of approximately 0.30 μm to approximately 0.40 μm.In a device having an IPS mode, a suitable value is in the range ofapproximately 0.20 μm to approximately 0.30 μm. In this case, acomposition having a large optical anisotropy is desirable for a devicehaving a small cell gap. The dielectric anisotropy having a largeabsolute value in the composition contributes to a low thresholdvoltage, a small electric power consumption and a high contrast ratio ofthe device. Accordingly, the dielectric anisotropy having a largeabsolute value is desirable. A large specific resistance of thecomposition contributes to a large voltage holding ratio and a largecontrast ratio of the device. Accordingly, a composition having a largespecific resistance is desirable at room temperature and also at a hightemperature in the initial stage. A composition having a large specificresistance is desirable at room temperature and also at a hightemperature after it has been used for a long time. The stability of thecomposition to ultraviolet light and heat relates to the service life ofthe liquid crystal display device. In the case where the stability ishigh, the device has a long service life. These characteristics aredesirable for an AM device used in a liquid crystal projector, a liquidcrystal television and so forth.

A composition having positive dielectric anisotropy is used for an AMdevice having a TN mode. On the other hand, a composition havingnegative dielectric anisotropy is used for an AM device having a VAmode. A composition having positive or negative dielectric anisotropy isused for an AM device having an IPS mode. A composition having positiveor negative dielectric anisotropy is used for an AM device having a PSAmode. Examples of the liquid crystal composition having negativedielectric anisotropy are disclosed in the following patent document No.1.

No. 1: WO 2009/034867 A.

A desirable AM device has characteristics such as a wide temperaturerange in which the device can be used, a short response time, a largecontrast ratio, a low threshold voltage, a large voltage holding ratioand a long service life. Response time that is one millisecond shorterthan that of the other devices is desirable. Thus, desirablecharacteristics of the composition includes a high maximum temperatureof a nematic phase, a low minimum temperature of a nematic phase, asmall viscosity, a suitable optical anisotropy, a positively ornegatively large dielectric anisotropy, a large specific resistance, ahigh stability to ultraviolet light and a high stability to heat.

SUMMARY OF THE INVENTION

The invention concerns a liquid crystal composition that has negativedielectric anisotropy and includes two components, wherein a firstcomponent is at least one compound selected from the group of compoundsrepresented by formula (1), and a second component is at least onecompound selected from the group of compounds represented by formula(2), and concerns also a liquid crystal display device containing thiscomposition:

wherein R¹, R², R³ and R⁴ are each independently alkyl having 1 to 12carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons,or alkenyl having 2 to 12 carbons in which arbitrary hydrogen isreplaced by fluorine; the ring A and the ring B are each independently1,4-cyclohexylene or 1,4-phenylene; one of the ring C and the ring D is2,3-difluoro-1,4-phenylene and the other is 1,4-cyclohexylene or1,4-phenylene; Z¹ and Z³ are each independently a single bond, ethyleneor difluoromethyleneoxy; and Z² is methyleneoxy, difluoromethyleneoxy orcarbonyloxy.

DETAILED DESCRIPTION OF THE INVENTION

The terms used in the specification and claims are defined as follows.The liquid crystal composition and the liquid crystal display device ofthe invention may occasionally be abbreviated to “the composition” and“the device,” respectively. “A liquid crystal display device” is ageneric term for a liquid crystal display panel and a liquid crystaldisplay module. “A liquid crystal compound” is a generic term for acompound having a liquid crystal phase such as a nematic phase and asmectic phase, and also for a compound having no liquid crystal phasesbut being useful as a component of a composition. Such a compound has asix-membered ring such as 1,4-cyclohexylene and 1,4-phenylene, and arod-like molecular structure. An optically active compound and apolymerizable compound may occasionally be added to the composition.Even in the case where these compounds are liquid crystalline, thecompounds are classified as an additive herein. At least one compoundselected from the group of compounds represented by formula (1) mayoccasionally be abbreviated to “the compound (1).” “The compound (1)”means one compound, or two or more compounds represented by formula (1).The same rules apply to compounds represented by the other formulas.“Arbitrary hydrogen” means that not only the position of hydrogen butalso its number may be selected without specific restriction.

A higher limit of the temperature range of a nematic phase mayoccasionally be abbreviated to “the maximum temperature.” A lower limitof the temperature range of a nematic phase may occasionally beabbreviated to “the minimum temperature.” That “specific resistance islarge” means that a composition has a large specific resistance at roomtemperature and also at a temperature close to the maximum temperatureof a nematic phase in the initial stage, and that the composition has alarge specific resistance at room temperature and also at a temperatureclose to the maximum temperature of a nematic phase even after it hasbeen used for a long time. That “a voltage holding ratio is large” meansthat a device has a large voltage holding ratio at room temperature andalso at a temperature close to the maximum temperature of a nematicphase in the initial stage, and that the device has a large voltageholding ratio at room temperature and also at a temperature close to themaximum temperature of a nematic phase even after it has been used for along time. When characteristics such as optical anisotropy areexplained, values that are measured according to the methods describedin Examples will be used. A first component means one compound, or twoor more compounds. “The ratio of the first component” is expressed as apercentage by weight (% by weight) of the first component based on thetotal weight of the liquid crystal composition. The same rule applies tothe ratio of a second component and so forth. The ratio of an additivemixed with the composition is expressed as a percentage by weight (% byweight) or weight parts per million (ppm) based on the total weight ofthe liquid crystal composition.

The symbol R¹ is used for a plurality of compounds in the chemicalformulas of component compounds. The meanings of R¹ may be the same ordifferent in arbitrary two compounds among these. In one case, forexample, R¹ of the compound (1) is ethyl and R¹ of the compound (1-1) isethyl. In another case, R¹ of the compound (1) is ethyl and R¹ of thecompound (1-1) is propyl. The same rule applies to the symbols R², Z¹and so forth.

One of the advantages of the invention is to provide a liquid crystalcomposition that satisfies at least one of characteristics such as ahigh maximum temperature of a nematic phase, a low minimum temperatureof a nematic phase, a small viscosity, a suitable optical anisotropy, anegatively large dielectric anisotropy, a large specific resistance, ahigh stability to ultraviolet light and a high stability to heat.Another advantage of the invention is to provide a liquid crystalcomposition that is suitably balanced regarding at least two of thecharacteristics, and a liquid crystal composition that in particularsatisfies a high maximum temperature and a small viscosity. A furtheradvantage of the invention is to provide a liquid crystal display devicethat contains such a composition. An additional advantage of theinvention is to provide a liquid crystal composition that has a suitableoptical anisotropy that is a large optical anisotropy or a small opticalanisotropy, a negatively large dielectric anisotropy, a high stabilityto ultraviolet light and so forth, and is to provide an AM device thathas a short response time, a large voltage holding ratio, a largecontrast ratio, a long service life and so forth.

The liquid crystal composition of the invention satisfied at least oneof characteristics such as a high maximum temperature of a nematicphase, a low minimum temperature of a nematic phase, a small viscosity,a suitable optical anisotropy, a negatively large dielectric anisotropy,a large specific resistance, a high stability to ultraviolet light and ahigh stability to heat. The liquid crystal composition was suitablybalanced regarding at least two of the characteristics. The liquidcrystal display device contained such a composition. The liquid crystalcomposition had a suitable optical anisotropy, a negatively largedielectric anisotropy, a high stability to ultraviolet light and soforth, and the AM device had a short response time, a large voltageholding ratio, a large contrast ratio, a long service life and so forth.

The invention includes the following items.

Item 1. A liquid crystal composition that has negative dielectricanisotropy and includes two components, wherein a first component is atleast one compound selected from the group of compounds represented byformula (1), and a second component is at least one compound selectedfrom the group of compounds represented by formula (2):

wherein R¹, R², R³ and R⁴ are each independently alkyl having 1 to 12carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons,or alkenyl having 2 to 12 carbons in which arbitrary hydrogen isreplaced by fluorine; the ring A and the ring B are each independently1,4-cyclohexylene or 1,4-phenylene; one of the ring C and the ring D is2,3-difluoro-1,4-phenylene and the other is 1,4-cyclohexylene or1,4-phenylene; Z¹ and Z³ are each independently a single bond, ethyleneor difluoromethyleneoxy; and Z² is methyleneoxy, difluoromethyleneoxy orcarbonyloxy.

Item 2. The liquid crystal composition according to item 1, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-1) to formula (1-6):

wherein R¹ and R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.

Item 3. The liquid crystal composition according to item 2, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-1).

Item 4. The liquid crystal composition according to claim 2, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-2).

Item 5. The liquid crystal composition according to any one of items 1to 4, wherein the ratio of the first component is in the range ofapproximately 5% to approximately 40% by weight and the ratio of thesecond component is in the range of approximately 10% to approximately95% by weight, based on the total weight of the liquid crystalcomposition.

Item 6. The liquid crystal composition according to any one of items 1to 5, further including at least one compound selected from the group ofcompounds represented by formula (3) as a third component:

wherein R⁵ and R⁶ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine; the ring E is independently 1,4-cyclohexylene,1,4-phenylene, tetrahydropyran-2,5-diyl, 2-fluoro-1,4-phenylene or2,3-difluoro-1,4-phenylene; Z⁴ is independently a single bond, ethylene,methyleneoxy or carbonyloxy; X¹ and X² are each independently fluorineor chlorine; Y¹ is hydrogen or methyl; and p is 1 or 2, q is 0 or 1, andthe sum of p and q is 2 or less.

Item 7. The liquid crystal composition according to item 6, wherein thethird component is at least one compound selected from the group ofcompounds represented by formula (3-1) to formula (3-20):

wherein R⁵ and R⁶ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.

Item 8. The liquid crystal composition according to item 7, wherein thethird component is at least one compound selected from the group ofcompounds represented by formula (3-1).

Item 9. The liquid crystal composition according to item 7, wherein thethird component is at least one compound selected from the group ofcompounds represented by formula (3-2) and at least one compoundselected from the group of compounds represented by formula (3-5).

Item 10. The liquid crystal composition according to item 7, wherein thethird component is at least one compound selected from the group ofcompounds represented by formula (3-14).

Item 11. The liquid crystal composition according to item 7, wherein thethird component is at least one compound selected from the group ofcompounds represented by formula (3-16) to formula (3-19).

Item 12. The liquid crystal composition according to any one of items 6to 11, wherein the ratio of the third component is in the range ofapproximately 10% to approximately 70% by weight based on the totalweight of the liquid crystal composition.

Item 13. The liquid crystal composition according to any one of items 1to 12, further including at least one compound selected from the groupof compounds represented by formula (4) as a fourth component:

wherein R⁷ and R⁸ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine; the ring F, the ring G and the ring I are eachindependently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenyleneor 3-fluoro-1,4-phenylene; Z⁵ and Z⁶ are each independently a singlebond, ethylene, methyleneoxy or carbonyloxy; r is 0, 1 or 2; and whereinat least one of the ring G and the ring I is 1,4-phenylene when r is 0.

Item 14. The liquid crystal composition according to item 13, whereinthe fourth component is at least one compound selected from the group ofcompounds represented by formula (4-1) to formula (4-12):

wherein R⁷ and R⁸ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.

Item 15. The liquid crystal composition according to item 14, whereinthe fourth component is at least one compound selected from the group ofcompounds represented by formula (4-4).

Item 16. The liquid crystal composition according to item 14, whereinthe fourth component is at least one compound selected from the group ofcompounds represented by formula (4-7).

Item 17. The liquid crystal composition according to any one of items 13to 16, wherein the ratio of the fourth component is in the range ofapproximately 5% to approximately 40% by weight based on the totalweight of the liquid crystal composition.

Item 18. The liquid crystal composition according to any one of items 1to 17, further including at least one compound selected from the groupof compounds represented by formula (5) as a fifth component:

wherein R⁹ and R¹⁰ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine; the ring J and the ring K are each independently1,4-cyclohexylene, 1,4-phenylene, tetrahydropyran-2,5-diyl or2,3-difluoro-1,4-phenylene; Z⁷ and Z⁸ are each independently a singlebond, ethylene, methyleneoxy or carbonyloxy; and s and t are eachindependently 0, 1, 2 or 3, and the sum of s and t is 3 or less.

Item 19. The liquid crystal composition according to item 18, whereinthe fifth component is at least one compound selected from the group ofcompounds represented by formula (5-1) to formula (5-5):

wherein R⁹ and R¹⁰ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.

Item 20. The liquid crystal composition according to item 19, whereinthe fifth component is at least one compound selected from the group ofcompounds represented by formula (5-4).

Item 21. The liquid crystal composition according to any one of items 18to 20, wherein the ratio of the fifth component is in the range ofapproximately 5% to approximately 30% by weight based on the totalweight of the liquid crystal composition.

Item 22. The liquid crystal composition according to any one of items 1to 21, wherein the maximum temperature of a nematic phase isapproximately 70° C. or higher, the optical anisotropy (25° C.) at awavelength of 589 nanometers is approximately 0.08 or more, and thedielectric anisotropy (25° C.) at a frequency of 1 kHz is approximately−2 or less.

Item 23. A liquid crystal display device containing the liquid crystalcomposition according to any one of items 1 to 22.

Item 24. The liquid crystal display device according to item 23, whereinan operating mode of the liquid crystal display device is a VA mode, anIPS mode or a PSA mode, and a driving mode of the liquid crystal displaydevice is an active matrix mode.

The invention further includes the following items: (1) the compositiondescribed above that further includes an optically active compound; (2)the composition described above that further includes an additive, suchas an antioxidant, an ultraviolet light absorbent and/or an antifoamingagent; (3) an AM device that includes the composition described above;(4) a device having a mode of TN, ECB, OCB, IPS, VA or PSA andcontaining the composition described above; (5) a device that has atransmission type and includes the composition described above; (6) useof the composition described above as a composition having a nematicphase; and (7) use as an optically active composition by adding anoptically active compound to the composition described above.

The composition of the invention will be explained in the followingorder. First, the constitution of component compounds in the compositionwill be explained. Second, main characteristics of the componentcompounds and main effects of the component compounds on the compositionwill be explained. Third, a combination of components in thecomposition, desirable ratios of the components and the basis thereofwill be explained. Fourth, a desirable embodiment of the componentcompounds will be explained. Fifth, examples of the component compoundswill be shown. Sixth, additives that may be mixed with the compositionwill be explained. Seventh, methods for synthesizing the componentcompounds will be explained. Last, use of the composition will beexplained.

First, the constitution of component compounds in the composition willbe explained. The compositions of the invention are classified into thecomposition A and the composition B. In addition to the compound (1),the compound (2), the compound (3), the compound (4) and the compound(5), the composition A may include any other liquid crystal compound, anadditive, an impurity and so forth. “Any other liquid crystal compound”is different from the compound (1), the compound (2), the compound (3),the compound (4) and the compound (5). Such a compound is mixed with thecomposition for the purpose of further adjusting characteristics of thecomposition. Of any other liquid crystal compound, a smaller amount of acyano compound is desirable in view of its stability to heat orultraviolet light. A more desirable ratio of the cyano compound is 0% byweight. The additive includes an optically active compound, anantioxidant, an ultraviolet light absorbent, a coloring matter, anantifoaming agent, a polymerizable compound and a polymerizationinitiator. The impurity is a compound and so forth which contaminatedthe component compounds in a process such as their synthesis. Even inthe case where the compound is liquid crystalline, it is classified intoan impurity herein.

The composition B consists essentially of compounds selected from thegroup of the compound (1), the compound (2), the compound (3), thecompound (4) and the compound (5). The term “essentially” means that thecomposition may include an additive and an impurity, but does notinclude any liquid crystal compound other than these compounds. Thecomposition B has a smaller number of components than the composition A.The composition B is preferable to the composition A in view of costreduction. The composition A is preferable to the composition B in viewof the fact that characteristics can be further adjusted by adding anyother liquid crystal compound.

Second, main characteristics of the component compounds and main effectsof the component compounds on the characteristics of the compositionwill be explained. The main characteristics of the component compoundsare summarized in Table 2 on the basis of the effects of the invention.In Table 2, the symbol L stands for “large” or “high”, the symbol Mstands for “medium”, and the symbol S stands for “small” or “low.” Thesymbols L, M and S are classified on the basis of a qualitativecomparison among the component compounds, and 0 (zero) means that “avalue is nearly zero.”

TABLE 2 Characteristics of Compounds Compounds Com- Com- pound poundCom- Compound Compound (1) (2) pound (3) (4) (5) Maximum L M M-L S-L MTemperature Viscosity M-L S M-L S-M L Optical M-L S M-L M-L M AnisotropyDielectric M-L 0 M-L 0 L Anisotropy Specific L L L L L Resistance

Main effects of the component compounds on the characteristics of thecomposition upon mixing the component compounds with the composition areas follows. The compound (1) increases the maximum temperature andincreases the absolute value of the dielectric anisotropy. The compound(2) decreases the viscosity. The compound (3) increases the absolutevalue of the dielectric anisotropy and decreases the minimumtemperature. The compound (4) decreases the viscosity, adjusts opticalanisotropy suitably, and decreases the minimum temperature. The compound(5) increases the absolute value of the dielectric anisotropy.

Third, a combination of the components in the composition, desirableratios of the components and the basis thereof will be explained. Thecombinations of the components in the composition is the first andsecond components, the first, second and third components, the first,second and fourth components, the first, second and fifth components,the first, second, third and fourth components, the first, second, thirdand fifth components, the first, second, fourth and fifth components,and the first, second, third, fourth and fifth components.

A desirable combination of the components in the composition is thefirst and second components for increasing the maximum temperature; thefirst, second and third components for increasing the absolute value ofthe dielectric anisotropy, for decreasing the viscosity or fordecreasing the minimum temperature; the first, second, third and fourthcomponents for increasing the absolute value of the dielectricanisotropy, for decreasing the viscosity or for adjusting opticalanisotropy suitably; the first, second, third, fourth and fifthcomponents for increasing the absolute value of the dielectricanisotropy. An especially desirable combination is the first, second,third and fourth components for decreasing the viscosity.

A desirable ratio of the first component is approximately 5% by weightor more for increasing the absolute value of the dielectric anisotropy,and is approximately 40% by weight or less for decreasing the minimumtemperature. Amore desirable ratio is in the range of approximately 10%to approximately 35% by weight. An especially desirable ratio is in therange of approximately 15% to approximately 30% by weight.

A desirable ratio of the second component is approximately 10% by weightor more for decreasing the viscosity, and is approximately 95% by weightor less for decreasing the minimum temperature. Amore desirable ratio isin the range of approximately 20% to approximately 70% by weight fordecreasing the viscosity. An especially desirable ratio is in the rangeof approximately 30% to approximately 60% by weight.

A desirable ratio of the third component is approximately 10% by weightor more for increasing the absolute value of the dielectric anisotropy,and is approximately 70% by weight or less for decreasing the minimumtemperature. Amore desirable ratio is in the range of approximately 20%to approximately 60% by weight. An especially desirable ratio is in therange of approximately 30% to approximately 50% by weight.

A desirable ratio of the fourth component is approximately 5% by weightor more for decreasing the viscosity, and is approximately 40% by weightor less for decreasing the minimum temperature. Amore desirable ratio isin the range of approximately 10% to approximately 35% by weight. Anespecially desirable ratio is in the range of approximately 15% toapproximately 30% by weight.

A desirable ratio of the fifth component is approximately 5% by weightor more for increasing the absolute value of the dielectric anisotropy,and is approximately 30% by weight or less for decreasing the minimumtemperature. Amore desirable ratio is in the range of approximately 10%to approximately 25% by weight. An especially desirable ratio is in therange of approximately 15% to approximately 20% by weight.

Fourth, a desirable embodiment of the component compounds will beexplained. R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are eachindependently alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine.

Desirable R¹, R², R³, R⁴, R⁷, R⁸, R⁹ or R¹⁰ is alkyl having 1 to 12carbons or alkenyl having 2 to 12 carbons for decreasing the minimumtemperature or for decreasing the viscosity. Desirable R⁵ or R⁶ is alkylhaving 1 to 12 carbons for decreasing the minimum temperature or fordecreasing the viscosity, and alkoxy having 1 to 12 carbons forincreasing the absolute value of the dielectric anisotropy. Moredesirable R¹, R², R³, R⁴, R⁵, R⁷, R⁸, R⁹ or R¹⁰ is alkyl having 1 to 12carbons for increasing the stability to ultraviolet light or heat.

Desirable alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptylor octyl. More desirable alkyl is ethyl, propyl, butyl, pentyl or heptylfor decreasing the viscosity.

Desirable alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy or heptyloxy. More desirable alkoxy is methoxy or ethoxy fordecreasing the viscosity.

Desirable alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl or 5-hexenyl. More desirablealkenyl is vinyl, 1-propenyl, 3-butenyl or 3-pentenyl for decreasing theviscosity. A desirable configuration of —CH═CH— in the alkenyl dependson the position of the double bond. Trans is preferable in the alkenylsuch as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl and3-hexenyl for decreasing the viscosity and for something. C ispreferable in the alkenyl such as 2-butenyl, 2-pentenyl and 2-hexenyl.In the alkenyl, straight-chain alkenyl is preferable to branched-chainalkenyl.

Desirable examples of alkenyl in which arbitrary hydrogen is replaced byfluorine are 2,2-difluorovinyl, 3,3-difluoro-2-propenyl,4,4-difluoro-3-butenyl, 5,5-difluoro-4-pentenyl and6,6-difluoro-5-hexenyl. More desirable examples are 2,2-difluoro-vinyland 4,4-difluoro-3-butenyl for decreasing the viscosity.

p is 1 or 2, q is 0 or 1, and the sum of p and q is 2 or less. Desirablep is 2 for increasing the maximum temperature, and is 1 for decreasingthe viscosity. Desirable q is 1 for increasing the maximum temperature,and is 0 for decreasing the minimum temperature. r is 0, 1 or 2.Desirable r is 1 or 2 for increasing the maximum temperature, and is 0for decreasing the viscosity. s and t are each independently 0, 1, 2 or3, and the sum of s and t is 3 or less. Desirable s or t is 2 or 3 forincreasing the maximum temperature, and is 1 for decreasing theviscosity.

The ring A and the ring B are each independently 1,4-cyclohexylene and1,4-phenylene. Desirable ring A or ring B is 1,4-cyclohexylene forincreasing the maximum temperature and 1,4-phenylene for increasing theoptical anisotropy. One of the ring C and the ring D is2,3-difluoro-1,4-phenylene, and the other is 1,4-cyclohexylene or1,4-phenylene. Desirable ring C or ring D is 1,4-cyclohexylene forincreasing the maximum temperature, and 1,4-phenylene for increasing theoptical anisotropy. Especially desirable ring C is2,3-difluoro-1,4-phenylene for increasing the dielectric anisotropy, andespecially desirable ring D is 1,4-cyclohexylene for increasing themaximum temperature. The ring E is 1,4-cyclohexylene, 1,4-phenylene,tetrahydropyran-2,5-diyl, 2-fluoro-1,4-phenylene or2,3-difluoro-1,4-phenylene, and arbitrary two of the ring E may be thesame or different when p is 2. Desirable ring E is 1,4-cyclohexylene forincreasing the maximum temperature, and tetrahydropyran-2,5-diyl or2,3-difluoro-1,4-phenylene for increasing the dielectric anisotropy. Thering F, the ring G and the ring I are each independently1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene or3-fluoro-1,4-phenylene, and arbitrary two of the ring F may be the sameor different when r is 2, and at least one of the ring G and the ring Iis 1,4-phenylene when r is 0. Desirable ring F, ring G or ring I is1,4-cyclohexylene for increasing the maximum temperature or fordecreasing the viscosity, and 1,4-phenylene for increasing the opticalanisotropy. The ring J and the ring K are each independently1,4-cyclohexylene, 1,4-phenylene, tetrahydropyran-2,5-diyl or2,3-difluoro-1,4-phenylene, and arbitrary two of the ring J may be thesame or different when s is 2 or 3, and arbitrary two of the ring J maybe the same or different when t is 2 or 3. Desirable ring J or ring K is1,4-cyclohexylene for increasing the maximum temperature or fordecreasing the viscosity, and 1,4-phenylene for increasing the opticalanisotropy. With regard to the configuration of 1,4-cyclohexylene, transis preferable to cis for increasing the maximum temperature.

X¹ and X² are each independently fluorine or chlorine. Desirable X¹ orX² is fluorine for decreasing the viscosity.

Y¹ is hydrogen or methyl. Desirable Y¹ is hydrogen for decreasing theviscosity, and methyl for increasing the stability to ultraviolet lightor heat.

Z¹ and Z³ are each independently a single bond, ethylene ordifluoromethyleneoxy. Desirable Z¹ or Z³ is a single bond for decreasingthe viscosity. Z² is methyleneoxy, difluoromethyleneoxy or carbonyloxy.Desirable Z² is carbonyloxy for increasing the maximum temperature, andmethyleneoxy for decreasing the minimum temperature. Z⁴ is a singlebond, ethylene, methyleneoxy or carbonyloxy, and arbitrary two of Z⁴ maybe the same or different when p is 2. Desirable Z⁴ is a single bond fordecreasing the viscosity, and methyleneoxy for increasing the dielectricanisotropy. Z⁵ and Z⁶ are each independently a single bond, ethylene,methyleneoxy or carbonyloxy, and arbitrary two of Z⁵ may be the same ordifferent when r is 2. Desirable Z⁵ or Z⁶ is a single bond fordecreasing the viscosity, and carbonyloxy for increasing the maximumtemperature. Z⁷ and Z⁸ are each independently a single bond, ethylene,methyleneoxy or carbonyloxy, and arbitrary two of Z⁷ or Z⁸ may be thesame or different when s or t is 2 or 3. Desirable Z⁷ is a single bondfor decreasing the viscosity, and methyleneoxy for increasing thedielectric anisotropy. Desirable Z⁸ is a single bond for decreasing theviscosity, and ethylene for decreasing the minimum temperature.

Fifth, examples of the component compounds will be shown. In thedesirable compounds described below, R¹¹, R¹², R¹⁶ and R¹⁷ are eachindependently alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons. R¹³ and R¹⁴ are eachindependently straight-chain alkyl having 1 to 12 carbons or alkoxyhaving 1 to 12 carbons. R¹⁵ is straight-chain alkenyl having 2 to 12carbons.

Desirable compound (1) are the compound (1-1-1) to the compound (1-6-1).More desirable compound (1) are the compound (1-1-1) and the compound(1-2-1). Desirable compound (2) are the compound (2-1) and the compound(2-2). More desirable compound (2) is the compound (2-2). Desirablecompound (3) are the compound (3-1-1) to the compound (3-20-1). Moredesirable compound (3) are the compound (3-1-1) to the compound (3-5-1),and the compound (3-9-1) to the compound (3-19-1). Especially desirablecompound (3) are the compound (3-1-1), the compound (3-3-1), thecompound (3-5-1), the compound (3-14-1), the compound (3-16-1) and thecompound (3-17-1). Desirable compound (4) are the compound (4-1-1) tothe compound (4-12-1). More desirable compound (4-4-1) are the compound(4-6-1) to the compound (4-12-1). Especially desirable compound (4) arethe compound (4-4-1), the compound (4-7-1) and the compound (4-10-1).Desirable compound (5) are the compound (5-1-1) to the compound (5-5-1).Especially desirable compound (5) is the compound (5-4-1).

Sixth, additives which may be mixed with the composition will beexplained. The additives include an optically active compound, anantioxidant, an ultraviolet light absorbent, a coloring matter, anantifoaming agent, a polymerizable compound and a polymerizationinitiator. The optically active compound is mixed into the compositionfor the purpose of inducing a helical structure and giving a twist anglein liquid crystals. Examples of such a compound include the compound(6-1) to the compound (6-4). A desirable ratio of the optically activecompound is approximately 5% by weight or less, and a more desirableratio is in the range of approximately 0.01% to approximately 2% byweight.

An antioxidant is mixed with the composition in order to prevent adecrease in specific resistance caused by heating under air, or tomaintain a large voltage holding ratio at room temperature and also at atemperature close to the maximum temperature of a nematic phase afterthe device has been used for a long time.

Desirable examples of the antioxidant include the compound (7) where wis an integer from 1 to 9. In the compound (7), desirable w is 1, 3, 5,7 or 9. More desirable w is 1 or 7. The compound (7) where w is 1 iseffective in preventing a decrease of specific resistance caused byheating under air because it has a large volatility. The compound (7)where w is 7 is effective in maintaining a large voltage holding ratioat room temperature and also at a temperature close to the maximumtemperature of a nematic phase after the device has been used for a longtime, because it has a small volatility. A desirable ratio of theantioxidant is approximately 50 ppm or more for achieving its effect andis approximately 600 ppm or less for avoiding a decrease of the maximumtemperature or avoiding an increase of the minimum temperature. A moredesirable ratio is in the range of approximately 100 ppm toapproximately 300 ppm.

Desirable examples of the ultraviolet light absorbent include abenzophenone derivative, a benzoate derivative and a triazolederivative. A light stabilizer such as an amine having steric hindranceis also desirable. A desirable ratio of the ultraviolet light absorbentor the light stabilizer is approximately 50 ppm or more for achievingits effect and is approximately 10,000 ppm or less for avoiding adecrease of the maximum temperature, or for avoiding an increase of theminimum temperature. Amore desirable ratio is in the range ofapproximately 100 ppm to approximately 10,000 ppm.

A dichroic dye such as an azo dye or an anthraquinone dye is mixed withthe composition for adjusting to a device having a guest host (GH) mode.A desirable ratio of the coloring matter is in the range ofapproximately 0.01% to approximately 10% by weight. An antifoaming agentsuch as dimethyl silicone oil or methyl phenyl silicone oil is mixedwith the composition for preventing foam formation. A desirable ratio ofthe antifoaming agent is approximately 1 ppm or more for achieving itseffect and is approximately 1,000 ppm or less for avoiding a poordisplay. A more desirable ratio is in the range of approximately 1 ppmto approximately 500 ppm.

A polymerizable compound is mixed with the composition for adjusting toa device having a polymer sustained alignment (PSA) mode. Desirableexamples of the polymerizable compound include compounds having apolymerizable group, such as acrylates, methacrylates, vinyl compounds,vinyloxy compounds, propenyl ethers, epoxy compounds (oxiranes,oxetanes) and vinyl ketones. Especially desirable examples of thepolymerizable compound are acrylate derivatives or methacrylatederivatives. A desirable ratio of the polymerizable compound isapproximately 0.05% by weight or more for achieving its effect and isapproximately 10% by weight or less for avoiding a poor display. A moredesirable ratio is in the range of approximately 0.1% to approximately2% by weight. The polymerizable compound is preferably polymerized onirradiation with ultraviolet light or the like in the presence of asuitable initiator such as a photopolymerization initiator. Suitableconditions for polymerization, suitable types of the initiator andsuitable amounts thereof are known to a person skilled in the art andare described in the literature. For example, Irgacure 651 (registeredtrademark), Irgacure 184 (registered trademark) or Darocure 1173(registered trademark) (Ciba Japan K.K.), each of which is aphotopolymerization initiator, is suitable for radical polymerization. Adesirable ratio of the photopolymerization initiator is in the range ofapproximately 0.1% to approximately 5% by weight based on the totalweight of the polymerizable compound. An especially desirable ratio isin the range of approximately 1% to approximately 3% by weight.

Seventh, methods for synthesizing the component compounds will beexplained. These compounds can be synthesized by known methods. Thesynthetic methods will be exemplified as follows. The compound (1-1-1)is prepared by the method described in WO 2009/034867 A. The compound(2-1) is prepared by the method described in JP S59-070624 A (1984). Thecompound (3-1-1) is prepared by the method described in JP H02-503441 A(1990). The compound (4-6-1) is prepared by the method described in JP2006-503130 A (2006). The compound (5-4-1) is prepared by the methoddescribed in JP 2005-290349 A (2005). An antioxidant is commerciallyavailable. The compound of formula (7) where w is 1 is available fromSigma-Aldrich Corporation. The compound (7) where w is 7, and so forthare prepared according to the method described in U.S. Pat. No.3,660,505.

Compounds whose synthetic methods are not described above can beprepared according to the methods described in books such as OrganicSyntheses (John Wiley & Sons, Inc.), Organic Reactions (John Wiley &Sons, Inc.), Comprehensive Organic Synthesis (Pergamon Press), NewExperimental Chemistry Course (Shin Jikken Kagaku Kouza, in Japanesetitle; Maruzen Co., Ltd.). The composition is prepared according toknown methods using the compounds thus obtained. For example, thecomponent compounds are mixed and dissolved each other by heating.

Last, use of the composition will be explained. Most of the compositionshave a minimum temperature of approximately −10° C. or lower, a maximumtemperature of approximately 70° C. or higher, and an optical anisotropyin the range of approximately 0.07 to approximately 0.20. The devicecontaining this composition has a large voltage holding ratio. Thecomposition is suitable for an AM device. The composition is suitableespecially for an AM device having a transmission type. The compositionhaving an optical anisotropy in the range of approximately 0.08 toapproximately 0.25 may be prepared by adjusting ratios of the componentcompounds or by mixing with any other liquid crystal compound. Thecomposition can be used as an optically active composition by theaddition of an optically active compound.

The composition can be used for an AM device. It can also be used for aPM device. The composition can be used for the AM device and the PMdevice having a mode such as PC, TN, STN, ECB, OCB, IPS, VA or PSA. Itis especially desirable to use the composition for the AM device havingthe IPS or VA mode. These devices may be of a reflection type, atransmission type or a semi-transmission type. It is desirable to usethe composition for a device having the transmission type. It can beused for an amorphous silicon-TFT device or a polycrystal silicon-TFTdevice. The composition is also usable for a nematic curvilinear alignedphase (NCAP) device prepared by microcapsulating the composition, andfor a polymer dispersed (PD) device in which a three-dimensionalnetwork-polymer is formed in the composition.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the invention and specificexamples provided herein without departing from the spirit or scope ofthe invention. Thus, it is intended that the invention covers themodifications and variations of this invention that come within thescope of any claims and their equivalents.

The following examples are for illustrative purposes only and are notintended, nor should they be interpreted, to limit the scope of theinvention.

EXAMPLES

A composition and a compound that will be included in the compositionwere a subject for measurement in order to evaluate the composition andthe compound. When the subject for measurement was a composition, thecomposition itself was measured as a sample, and the value obtained wasdescribed here. When the subject for measurement was a compound, asample for measurement was prepared by mixing the compound (15% byweight) with mother liquid crystals (85% by weight). Characteristicvalues of the compound were calculated from values obtained bymeasurement, according to a method of extrapolation. That is:(extrapolated value)=[(measured value of a sample)−0.85×(measured valueof mother liquid crystals)]/0.15. When a smectic phase (or crystals)separated out at this ratio at 25° C., the ratio of the compound to themother liquid crystals was changed step by step in the order of (10% byweight/90% by weight), (5% by weight/95% by weight) and (1% byweight/99% by weight). Values of the maximum temperature, the opticalanisotropy, the viscosity and the dielectric anisotropy with regard tothe compound were obtained by the extrapolation.

The components of the mother liquid crystals and their ratios were asfollows.

Characteristics were measured according to the following methods. Mostmethods are described in the Standards of Electronic IndustriesAssociation of Japan, EIAJ•ED-2521 A or those with some modifications.

Maximum Temperature of a Nematic Phase (NI; ° C.): A sample was placedon a hot plate in a melting point apparatus equipped with a polarizingmicroscope and was heated at the rate of 1° C. per minute. Temperaturewas measured when part of the sample began to change from a nematicphase to an isotropic liquid. A higher limit of the temperature range ofa nematic phase may occasionally be abbreviated to “the maximumtemperature.”

Minimum Temperature of a Nematic Phase (Tc; ° C.): A sample having anematic phase was put in glass vials and then kept in freezers attemperatures of 0° C., −10° C., −20° C., −30° C. and −40° C. for 10days, and then the liquid crystal phases were observed. For example,when the sample maintained the nematic phase at −20° C. and changed tocrystals or a smectic phase at −30° C., Tc was expressed as ≦−20° C. Alower limit of the temperature range of a nematic phase may occasionallybe abbreviated to “the minimum temperature.”

Viscosity (bulk viscosity; η; measured at 20° C.; mPa·s): Viscosity wasmeasured by use of an E-type viscometer.

Optical Anisotropy (refractive index anisotropy; Δn; measured at 25°C.): Measurement was carried out by use of an Abbe refractometer with apolarizing plate mounted on the ocular, on irradiation with light at awavelength of 589 nanometers. The surface of the main prism was rubbedin one direction, and then a sample was dropped on the main prism. Arefractive index (n∥) was measured when the direction of polarized lightwas parallel to that of the rubbing. A refractive index (n⊥) wasmeasured when the direction of polarized light was perpendicular to thatof the rubbing. The value of optical anisotropy was calculated from theequation: Δn=n∥−n⊥.

Dielectric Anisotropy (Δ∈; measured at 25° C.): The value of dielectricanisotropy was calculated from the equation: Δ∈=∈∥−∈⊥. Dielectricconstants (∈∥ and ∈⊥) were measured as follows.

(1) Measurement of a dielectric constant (∈∥): A solution ofoctadecyltriethoxysilane (0.16 mL) in ethanol (20 mL) was applied to athoroughly cleaned glass substrate. The glass substrate was rotated witha spinner, and then heated at 150° C. for one hour. A sample was pouredinto a VA device in which the distance between two glass substrates(cell gap) was 4 micrometers, and then the device was sealed with anadhesive curable on irradiation with ultraviolet light. Sine waves (0.5V, 1 kHz) were applied to the device, and a dielectric constant (∈∥) ina major axis direction of liquid crystal molecules was measured after 2seconds.

(2) Measurement of a dielectric constant (∈⊥): A polyimide solution wasapplied to a thoroughly cleaned glass substrate. The glass substrate wasburned, and then the alignment film obtained was subjected to rubbingtreatment. A sample was poured into a TN device in which the distancebetween two glass substrates (cell gap) was 9 micrometers and the twistangle was 80 degrees. Sine waves (0.5 V, 1 kHz) were applied to thedevice, and a dielectric constant (∈⊥) in a minor axis direction ofliquid crystal molecules was measured after 2 seconds.

Threshold Voltage (Vth; measured at 25° C.; V): Measurement was carriedout with an LCD evaluation system Model LCD-5100 made by OtsukaElectronics Co., Ltd. The light source was a halogen lamp. A sample waspoured into a VA device having a normally black mode, in which thedistance between two glass substrates (cell gap) was 4 micrometers andrubbing directions were antiparallel, and then the device was sealedwith an adhesive curable on irradiation with ultraviolet light. Voltageto be applied to the device (60 Hz, rectangular waves) was stepwiseincreased in 0.02 V increments from 0 V up to 20 V. During the increase,the device was irradiated with light in the perpendicular direction, andthe amount of light passing through the device was measured. Avoltage-transmittance curve was prepared, in which the maximum amount oflight corresponded to 100% transmittance and the minimum amount of lightcorresponded to 0% transmittance. The threshold voltage was voltage at10% transmittance.

Voltage Holding Ratio (VHR-1; measured at 25° C.; %): A TN device usedfor measurement had a polyimide-alignment film, and the distance betweentwo glass substrates (cell gap) was 5 micrometers. A sample was pouredinto the device, and then the device was sealed with an adhesivepolymerizable on irradiation with ultraviolet light. A pulse voltage (60microseconds at 5 V) was applied to the TN device and the device wascharged. A decreasing voltage was measured for 16.7 milliseconds with ahigh-speed voltmeter, and the area A between a voltage curve and ahorizontal axis in a unit cycle was obtained. The area B was an areawithout the decrease. The voltage holding ratio was a percentage of thearea A to the area B.

Voltage Holding Ratio (VHR-2; measured at 80° C.; %): A TN device usedfor measurement had a polyimide-alignment film, and the distance betweentwo glass substrates (cell gap) was 5 micrometer. A sample was pouredinto the device, and then the device was sealed with an adhesivepolymerizable on irradiation with ultraviolet light. A pulse voltage (60microseconds at 5 V) was applied to the TN device and the device wascharged. A decreasing voltage was measured for 16.7 milliseconds with ahigh-speed voltmeter and the area A between a voltage curve and ahorizontal axis in a unit cycle was obtained. The area B was an areawithout the decrease. The voltage holding ratio was a percentage of thearea A to the area B.

Voltage Holding Ratio (VHR-3; measured at 25° C.; %): The stability toultraviolet light was evaluated by measuring a voltage holding ratioafter irradiation with ultraviolet light. A TN device used formeasurement had a polyimide-alignment film and the cell gap was 5micrometers. A sample was poured into the device, and then the devicewas irradiated with light for 20 minutes. The light source was an ultrahigh-pressure mercury lamp USH-500D (produced by Ushio, Inc.), and thedistance between the device and the light source was 20 centimeters. Inthe measurement of VHR-3, a decreasing voltage was measured for 16.7milliseconds. A composition having a large VHR-3 has a high stability toultraviolet light. The value of VHR-3 is preferably 90% or more, andmore preferably 95% or more.

Voltage Holding Ratio (VHR-4; measured at 25° C.; %): A TN device intowhich a sample was poured was heated in a constant-temperature bath at80° C. for 500 hours, and then the stability to heat was evaluated bymeasuring the voltage holding ratio. In the measurement of VHR-4, adecreasing voltage was measured for 16.7 milliseconds. A compositionhaving a large VHR-4 has a high stability to heat.

Response Time (τ; measured at 25° C.; millisecond): Measurement wascarried out with an LCD evaluation system Model LCD-5100 made by OtsukaElectronics Co., Ltd. The light source was a halogen lamp. The low-passfilter was set at 5 kHz. A sample was poured into a VA device having anormally black mode, in which the cell gap between two glass substrateswas 4 micrometers, and a rubbing direction was antiparallel, and thenthe device was sealed with an adhesive curable on irradiation withultraviolet light. Rectangular waves (60 Hz, 10 V, 0.5 second) wereapplied to the device. The device was simultaneously irradiated withlight in the perpendicular direction, and the amount of light passingthrough the device was measured. The maximum amount of lightcorresponded to 100% transmittance, and the minimum amount of lightcorresponded to 0% transmittance. The response time was the period oftime required for the change from 90% to 10% transmittance (fall time:millisecond).

Specific Resistance (ρ; measured at 25° C.; Ωcm): A sample of 1.0milliliter was poured into a vessel equipped with electrodes. DC voltage(10V) was applied to the vessel, and the DC current was measured after10 seconds. The specific resistance was calculated according to thefollowing equation: (specific resistance)=[(voltage)×(electric capacityof vessel)]/[(DC current)×(a dielectric constant in vacuum)].

Gas Chromatographic Analysis: A gas chromatograph Model GC-14B made byShimadzu Corporation was used for measurement. The carrier gas washelium (2 milliliters per minute). The sample injector and the detector(FID) were set to 280° C. and 300° C., respectively. A capillary columnDB-1 (length 30 meters, bore 0.32 millimeter, film thickness 0.25micrometer, dimethylpolysiloxane as the stationary phase, non-polar)made by Agilent Technologies, Inc. was used for the separation ofcomponent compounds. After the column had been kept at 200° C. for 2minutes, it was further heated to 280° C. at the rate of 5° C. perminute. A sample was dissolved in acetone (0.1% by weight), and 1microliter of the solution was injected into the sample injector. Arecorder used was a Model C-R5A Chromatopac Integrator made by ShimadzuCorporation or its equivalent. A gas chromatogram obtained showed theretention time of peaks and the peak areas corresponding to thecomponent compounds.

Solvents for diluting the sample may also be chloroform, hexane and soforth. The following capillary columns may also be used in order toseparate the component compounds: HP-1 made by Agilent Technologies Inc.(length 30 meters, bore 0.32 millimeter, film thickness 0.25micrometer), Rtx-1 made by Restek Corporation (length 30 meters, bore0.32 millimeter, film thickness 0.25 micrometer), and BP-1 made by SGEInternational Pty. Ltd. (length 30 meters, bore 0.32 millimeter, filmthickness 0.25 micrometer). A capillary column CBP1-M50-025 (length 50meters, bore 0.25 millimeter, film thickness 0.25 micrometer) made byShimadzu Corporation may also be used for the purpose of avoiding anoverlap of peaks of the compounds.

The ratio of the liquid crystal compounds included in the compositionmay be calculated according to the following method. The liquid crystalcompounds are detected by use of a gas chromatograph. The ratio of peakareas in the gas chromatogram corresponds to the ratio (molar ratio) ofthe liquid crystal compounds. When the capillary columns described aboveare used, the correction coefficient of respective liquid crystalcompounds may be regarded as one. Accordingly, the ratio (weight ratio)of the liquid crystal compound can be calculated from the ratio of peakareas.

The invention will be explained in detail by way of Examples. Theinvention is not limited by Examples described below. The compoundsdescribed in Comparative Examples and Examples were expressed as symbolsaccording to the definition in the following Table 3. In Table 3, theconfiguration of 1,4-cyclohexylene is trans. A parenthesized number nextto the symbolized compound in Example corresponds to a compound number.The symbol (−) means any other liquid crystal compound. Ratios(percentage) of liquid crystal compounds mean the percentages by weight(% by weight) based on the total weight of the liquid crystalcomposition. The liquid crystal composition further includes animpurity. Last, characteristics of the composition are summarized.

TABLE 3 Method of Description of Compounds using Symbols R—(A₁)—Z₁— . .. —Z_(n)—(A_(n))—R′ 1) Left-Terminal Group R— Symbol C_(n)H_(2n+1)— n-C_(n)H_(2n+1)O— nO— C_(m)H_(2m+1)OC_(n)H_(2n)— mOn- CH₂═CH— V—C_(n)H_(2n+1)—CH═CH— nV— CH₂═CH—C_(n)H_(2n)— Vn-C_(m)H_(2m+1)—CH═CH—C_(n)H_(2n)— mVn- CF₂═CH— VFF— CF₂═CH—C_(n)H_(2n)—VFFn- 2) Right-Terminal Group —R′ Symbol —C_(n)H_(2n+1) -n—OC_(n)H_(2n+1) —On —CH═CH₂ —V —CH═CH—C_(n)H_(2n+1) —Vn—C_(n)H_(2n)—CH═CH₂ -nV —CH═CF₂ —VFF —OC_(n)H_(2n)—CH═CH₂ —OnV 3)Bonding Group —Z_(n)— Symbol —CF₂O— X —C_(n)H_(2n)— n —COO— E —CH═CH— V—CH₂O— 1O —OCH₂— O1 —SiH₂— Si 4) Ring Structure —A_(n)— Symbol

H

ch

B

B(2F)

B(2CL)

B(F)

B(2F,3F)

B(2F,3CL)

B(2CL,3F)

B(3F,6F)

B(2F,3F,6Me)

dh

Dh

Cro(7F,8F) 5) Examples of Description

Comparative Example 1

The composition in Composition Example 4 was selected from thecompositions disclosed in WO 2009/034867 A (the patent document No. 1).The basis of the selection was that the composition included thecompound (1-1-1), the compound (1-3-1), the compound (3-2-1), thecompound (3-5-1), the compound (4-1-1) and the compound (4-4-1), and hadthe smallest viscosity. Since the bulk viscosity of the composition wasnot described, the inventors prepared the composition and measuredaccording to the above method. The composition had the followingcomponents and characteristics.

5-HH1OB(2F,3F)H-3 (1-1-1) 6% 5-HH1OB(2F,3F)B-3 (1-3-1) 5%3-H2B(2F,3F)-O2 (3-2-1) 18% 5-H2B(2F,3F)-O2 (3-2-1) 19% 3-HBB(2F,3F)-O2(3-5-1) 7% 5-HBB(2F,3F)-O2 (3-5-1) 8% 3-HB-O2 (4-1-1) 7% 3-HHB-1 (4-4-1)5% V2-HHB-1 (4-4-1) 3% 3-HHB-O1 (4-4-1) 5% 3-H2H-V (—) 17%

-   -   NI=81.4° C.; Tc≦20° C.; Δn=0.096; η=22.3 mPa·s; Δ∈=−3.4.

Example 1

3-HH1OB(2F,3F)H-5 (1-1-1) 5% 5-HH1OB(2F,3F)H-3 (1-1-1) 5% 3-HH-V (2-2)30% 3-H2B(2F,3F)-O2 (3-2-1) 10% 5-H2B(2F,3F)-O2 (3-2-1) 20%2-HHB(2F,3F)-O2 (3-3-1) 8% 3-HHB(2F,3F)-O2 (3-3-1) 5% 1V2-HHB(2F,3F)-O2(3-3-1) 7% 3-HBB(2F,3F)-O2 (3-5-1) 5% 5-HBB(2F,3F)-O2 (3-5-1) 5%

-   -   NI=83.2° C.; Tc≦−20° C.; Δn=0.085; η=19.9 mPa·s; A s=−3.5;        VHR-1=99.2%; VHR-2=98.1%; VHR-3=97.9%.

Example 2

2-HH1OB(2F,3F)H-3 (1-1-1) 5% V-HH1OB(2F,3F)H-3 (1-1-1) 5% 3-HH-O1 (2-1)5% 3-HH-V (2-2) 28% 3-HH-V1 (2-2) 7% 5-HB(2F,3F)-O2 (3-1-1) 5%1V2-HB(2F,3F)-O2 (3-1-1) 7% 3-HHB(2F,3F)-1 (3-3-1) 5% 3-HHB(2F,3CL)-O2(3-6-1) 5% 3-H1OB(2F,3F)-O2 (3-13-1) 5% 3-HH1OB(2F,3F)-O2 (3-14-1) 5%5-HH1OB(2F,3F)-O2 (3-14-1) 8% 3-HH1OB(2F,3F)-1 (3-14-1) 3%3-HDhB(2F,3F)-O2 (3-17-1) 7%

-   -   NI=84.6° C.; Tc≦−20° C.; Δn=0.073; η=19.8 mPa·s; Δ∈=−3.4;        VHR-1=99.1%; VHR-2=98.0%; VHR-3=97.7%.

Example 3

5-HH1OB(2F,3F)H-O2 (1-1-1) 5% 5-HHEB(2F,3F)H-3 (1-2-1) 5%5-HHEB(2F,3F)H-O2 (1-2-1) 5% 2-HH-3 (2-1) 5% 3-HH-V (2-2) 7% 3-HH-V1(2-2) 10% 3-HH-VFF (2) 10% V-HB(2F,3F)-O2 (3-1-1) 5% 3-H2B(2F,3F)-O2(3-2-1) 10% 3-HHB(2F,3F)-1 (3-3-1) 7% 3-HH2B(2F,3F)-O2 (3-4-1) 10%3-HBB(2F,3CL)-O2 (3-7-1) 3% 3-HH2B(2F,3F,6Me)-O2 (3-8-1) 3%3-H1OB(2F,3F)-O2 (3-13-1) 5% 5-H1OB(2F,3F)-O2 (3-13-1) 10%

-   -   NI=82.8° C.; Tc≦−20° C.; Δn=0.076; η=19.7 mPa·s; Δ∈=−3.4;        VHR-1=99.2%; VHR-2=98.0%; VHR-3=98.0%.

Example 4

5-HH1OB(2F,3F)H-3 (1-1-1) 7% V-HH1OB(2F,3F)H-3 (1-1-1) 5%5-HH1OB(2F,3F)B-3 (1-3-1) 5% 3-HH-V (2-2) 30% 3-HH-V1 (2-2) 3%3-H2B(2F,3F)-O2 (3-2-1) 15% 2-HHB(2F,3F)-O2 (3-3-1) 5% 1V2-HHB(2F,3F)-O2(3-3-1) 5% 2O-B(2F)B(2F,3F)-O3 (3-9-1) 5% 3-HEB(2F,3F)B(2F,3F)-O2(3-12-1) 3% 3-H1OB(2F,3F)-O2 (3-13-1) 4% 3-HH1OB(2F,3F)-1 (3-14-1) 3%3-HB-O2 (4-1-1) 5% 3-HHB-1 (4-4-1) 5%

-   -   NI=83.5° C.; Tc≦−20° C.; Δn=0.083; η=18.3 mPa·s; Δ∈=−3.0;        VHR-1=99.3%; VHR-2=98.1%; VHR-3=98.1%.

Example 5

5-HH1OB(2F,3F)H-3 (1-1-1) 7% 5-HHEB(2F,3F)H-3 (1-2-1) 5%5-HHEB(2F,3F)B-3 (1-4-1) 3% 2-HH-3 (2-1) 10% 3-HH-V (2-2) 20% 3-HH-VFF(2) 5% 2-H1OB(2F,3F)-O2 (3-13-1) 5% 3-H1OB(2F,3F)-O2 (3-13-1) 7%V-H1OB(2F,3F)-O2 (3-13-1) 7% 5-HH1OB(2F,3F)-O2 (3-14-1) 5%5-DhB(2F,3F)-O2 (3-15-1) 3% 3-HDhB(2F,3F)-O2 (3-17-1) 5%3-DhH1OB(2F,3F)-O2 (3-18-1) 5% V-HHB-1 (4-4-1) 5% 3-HBB-2 (4-5-1) 3%2-BB(F)B-3 (4-6-1) 5%

-   -   NI=82.4° C.; Tc≦−20° C.; Δn=0.082; η=18.7 mPa·s; Δ∈=−3.2;        VHR-1=99.3%; VHR-2=98.1%; VHR-3=98.1%.

Example 6

V-HH1OB(2F,3F)H-3 (1-1-1) 6% 5-HHEB(2F,3F)B-3 (1-4-1) 6%5-HBEB(2F,3F)B-3 (1-6-1) 4% 2-HH-3 (2-1) 8% 3-HH-5 (2-1) 5% 3-HH-VFF (2)10% 3-H2B(2F,3F)-O2 (3-2-1) 10% 5-HH2B(2F,3F)-O2 (3-4-1) 12%2O-B(2F,3F)B(2F,3F)-O3 (3-10-1) 3% 3-H1OB(2F,3F)-O2 (3-13-1) 5%V-H1OB(2F,3F)-O2 (3-13-1) 10% V-BB-1 (4-2-1) 5% 1V2-BB-1 (4-2-1) 3%3-HHEH-5 (4-3-1) 3% 5-B(F)BB-2 (4-7-1) 5% 3-B(F)BB-2V (4-7-1) 5%

-   -   NI=83.1° C.; Tc≦−20° C.; Δn=0.109; η=18.7 mPa·s; Δ∈=−3.0;        VHR-1=99.1%; VHR-2=98.0%; VHR-3=98.0%.

Example 7

5-HHEB(2F,3F)H-O2 (1-2-1) 6% 5-HBEB(2F,3F)H-3 (1-5-1) 3%5-HHXB(2F,3F)B-3 (1) 3% 3-HH-V (2-2) 12% 3-HH-V1 (2-2) 5% V-HB(2F,3F)-O2(3-1-1) 3% 1V-HB(2F,3F)-O2 (3-1-1) 5% 3-H2B(2F,3F)-O2 (3-2-1) 21%3-HH2B(2F,3F)-O2 (3-4-1) 3% 2-BB(2F,3F)B-4 (3-11-1) 5% 2-H1OB(2F,3F)-O2(3-13-1) 5% V-H1OB(2F,3F)-O2 (3-13-1) 5% V-BB-1 (4-2-1) 10% 3-HHEBH-3(4-8-1) 5% 3-HBBH-3 (4-9-1) 3% 3-HB(F)BH-3 (4-11-1) 3% 5-HBB(F)B-2(4-12-1) 3%

-   -   NI=82.7° C.; Tc≦−20° C.; Δn=0.106; η=19.1 mPa·s; Δ∈=−3.0;        VHR-1=99.2%; VHR-2=98.1%; VHR-3=98.1%.

Example 8

5-HH1OB(2F,3F)H-3 (1-1-1) 5% 5-HH1OB(2F,3F)H-O2 (1-1-1) 5% 3-HH-V (2-2)28% 3-HH-V1 (2-2) 7% V-HB(2F,3F)-O3 (3-1-1) 4% 3-H2B(2F,3F)-O2 (3-2-1)8% 5-HH2B(2F,3F)-O2 (3-4-1) 12% V-H1OB(2F,3F)-O2 (3-13-1) 6%3-DhHB(2F,3F)-O2 (3-16-1) 5% 3-dhBB(2F,3F)-O2 (3-19-1) 5%3-HH1OB(2F,3F,6Me)-O2 (3-20-1) 3% 5-HB(2F,3CL)-O2 (3) 3% V-BB-1 (4-2-1)3% 3-HHEH-5 (4-3-1) 3% 1O1-HBBH-4 (—) 3%

-   -   NI=83.3° C.; Tc≦−20° C.; Δn=0.081; η=18.3 mPa·s; Δ∈=−3.0;        VHR-1=99.3%; VHR-2=98.2%; VHR-3=98.0%.

Example 9

V-HH1OB(2F,3F)H-3 (1-1-1) 3% 5-HHEB(2F,3F)H-3 (1-2-1) 7%5-HHEB(2F,3F)B-3 (1-4-1) 5% 3-HH-V (2-2) 27% 3-HH-V1 (2-2) 7%3-H2B(2F,3F)-O2 (3-2-1) 4% 2O-B(2F,3F)B(2F,3F)-O4 (3-10-1) 5%V-H1OB(2F,3F)-O2 (3-13-1) 5% 5-HH1OB(2F,3F)-O2 (3-14-1) 4% V-BB-1(4-2-1) 9% 1V2-BB-1 (4-2-1) 4% V2-BB(F)B-1 (4-6-1) 3% 5-HB(F)HH-V(4-10-1) 3% 3-H1OCro(7F,8F)-5 (5-2-1) 5% 3-HH2Cro(7F,8F)-5 (5-3-1) 3%3-HH1OCro(7F,8F)-5 (5-4-1) 3% 5-HB1OCro(7F,8F)-5 (5-5-1) 3%

-   -   NI=83.1° C.; Tc≦−20° C.; Δn=0.097; η=19.3 mPa·s; Δ∈=−3.1;        VHR-1=98.9%; VHR-2=97.9%; VHR-3=97.8%.

Example 10

V-HH1OB(2F,3F)H-3 (1-1-1) 7% 5-HH1OB(2F,3F)H-O2 (1-1-1) 3%5-BBEB(2F,3F)B-3 (1) 3% 2-HH-3 (2-1) 5% 3-HH-V (2-2) 19% 3-H2B(2F,3F)-O2(3-2-1) 20% 3-HH2B(2F,3F)-O2 (3-4-1) 8% 5-HH2B(2F,3F)-O2 (3-4-1) 8%5-HH1OB(2F,3F)-O2 (3-14-1) 3% V-BB-1 (4-2-1) 7% 3-HHB-1 (4-4-1) 4%V2-HHB-1 (4-4-1) 5% 5-H2Cro(7F,8F)-5 (5-1-1) 5% 4O-Cro(7F,8F)H-3 (5) 3%

-   -   NI=82.6° C.; Tc≦−20° C.; Δn=0.087; η=19.6 mPa·s; Δ∈=−3.1;        VHR-1=98.8%; VHR-2=97.9%; VHR-3=97.7%.

The compositions of Examples 1 to 10 had a high maximum temperature anda small viscosity in comparison with those in Comparative Example 1.Thus, it was found that the liquid crystal composition of the inventionwas so much superior in characteristics to that of the patent documentNo. 1.

APPLICABILITY TO INDUSTRY

The invention provides a liquid crystal composition that satisfies atleast one of characteristics such as a high maximum temperature of anematic phase, a low minimum temperature of a nematic phase, a smallviscosity, a suitable optical anisotropy, a negatively large dielectricanisotropy, a large specific resistance, a high stability to ultravioletlight and a high stability to heat, or that is suitably balancedregarding at least two of the characteristics. Thus, a liquid crystaldisplay device containing this composition can be used as an AM devicethat has a short response time, a large voltage holding ratio, a largecontrast ratio, a long service life and so forth, and can be used for aliquid crystal projector, a liquid crystal television and so forth.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the disclosure has beenmade only by way of example, and that numerous changes in the conditionsand order of steps can be resorted to by those skilled in the artwithout departing from the spirit and scope of the invention.

1. A liquid crystal composition that has negative dielectric anisotropyand comprises two components, wherein a first component is at least onecompound selected from the group of compounds represented by formula(1), and a second component is at least one compound selected from thegroup of compounds represented by formula (2):

wherein R¹, R², R³ and R⁴ are each independently alkyl having 1 to 12carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons,or alkenyl having 2 to 12 carbons in which arbitrary hydrogen isreplaced by fluorine; the ring A and the ring B are each independently1,4-cyclohexylene or 1,4-phenylene; one of the ring C and the ring D is2,3-difluoro-1,4-phenylene and the other is 1,4-cyclohexylene or1,4-phenylene; Z¹ and Z³ are each independently a single bond, ethyleneor difluoromethyleneoxy; and Z² is methyleneoxy, difluoromethyleneoxy orcarbonyloxy.
 2. The liquid crystal composition according to claim 1,wherein the first component is at least one compound selected from thegroup of compounds represented by formula (1-1) to formula (1-6):

wherein R¹ and R² are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.
 3. The liquid crystal composition according to claim 2,wherein the first component is at least one compound selected from thegroup of compounds represented by formula (1-1).
 4. The liquid crystalcomposition according to claim 2, wherein the first component is atleast one compound selected from the group of compounds represented byformula (1-2).
 5. The liquid crystal composition according to claim 1,wherein the ratio of the first component is in the range ofapproximately 5% to approximately 40% by weight and the ratio of thesecond component is in the range of approximately 10% to approximately95% by weight, based on the total weight of the liquid crystalcomposition.
 6. The liquid crystal composition according to claim 1,further comprising at least one compound selected from the group ofcompounds represented by formula (3) as a third component:

wherein R⁵ and R⁶ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine; the ring E is independently 1,4-cyclohexylene,1,4-phenylene, tetrahydropyran-2,5-diyl, 2-fluoro-1,4-phenylene or2,3-difluoro-1,4-phenylene; Z⁴ is independently a single bond, ethylene,methyleneoxy or carbonyloxy; X¹ and X² are each independently fluorineor chlorine; Y¹ is hydrogen or methyl; and p is 1 or 2, q is 0 or 1, andthe sum of p and q is 2 or less.
 7. The liquid crystal compositionaccording to claim 6, wherein the third component is at least onecompound selected from the group of compounds represented by formula(3-1) to formula (3-20):

wherein R⁵ and R⁶ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.
 8. The liquid crystal composition according to claim 7,wherein the third component is at least one compound selected from thegroup of compounds represented by formula (3-1).
 9. The liquid crystalcomposition according to claim 7, wherein the third component is atleast one compound selected from the group of compounds represented byformula (3-2) and at least one compound selected from the group ofcompounds represented by formula (3-5).
 10. The liquid crystalcomposition according to claim 7, wherein the third component is atleast one compound selected from the group of compounds represented byformula (3-14).
 11. The liquid crystal composition according to claim 7,wherein the third component is at least one compound selected from thegroup of compounds represented by formula (3-16) to formula (3-19). 12.The liquid crystal composition according to claim 6, wherein the ratioof the third component is in the range of approximately 10% toapproximately 70% by weight based on the total weight of the liquidcrystal composition.
 13. The liquid crystal composition according toclaim 6, further comprising at least one compound selected from thegroup of compounds represented by formula (4) as a fourth component:

wherein R⁷ and R⁸ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine; the ring F, the ring G and the ring I are eachindependently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenyleneor 3-fluoro-1,4-phenylene; Z⁵ and Z⁶ are each independently a singlebond, ethylene, methyleneoxy or carbonyloxy; r is 0, 1 or 2; and whereinat least one of the ring G and the ring I is 1,4-phenylene when r is 0.14. The liquid crystal composition according to claim 13, wherein thefourth component is at least one compound selected from the group ofcompounds represented by formula (4-1) to formula (4-12):

wherein R⁷ and R⁸ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.
 15. The liquid crystal composition according to claim 14,wherein the fourth component is at least one compound selected from thegroup of compounds represented by formula (4-4).
 16. The liquid crystalcomposition according to claim 14, wherein the fourth component is atleast one compound selected from the group of compounds represented byformula (4-7).
 17. The liquid crystal composition according to claim 13,wherein the ratio of the fourth component is in the range ofapproximately 5% to approximately 40% by weight based on the totalweight of the liquid crystal composition.
 18. The liquid crystalcomposition according to claim 13, further comprising at least onecompound selected from the group of compounds represented by formula (5)as a fifth component:

wherein R⁹ and R¹⁰ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine; the ring J and the ring K are each independently1,4-cyclohexylene, 1,4-phenylene, tetrahydropyran-2,5-diyl or2,3-difluoro-1,4-phenylene; Z⁷ and Z⁸ are each independently a singlebond, ethylene, methyleneoxy or carbonyloxy; and s and t are eachindependently 0, 1, 2 or 3, and the sum of s and t is 3 or less.
 19. Theliquid crystal composition according to claim 18, wherein the fifthcomponent is at least one compound selected from the group of compoundsrepresented by formula (5-1) to formula (5-5):

wherein R⁹ and R¹⁰ are each independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, oralkenyl having 2 to 12 carbons in which arbitrary hydrogen is replacedby fluorine.
 20. The liquid crystal composition according to claim 19,wherein the fifth component is at least one compound selected from thegroup of compounds represented by formula (5-4).
 21. The liquid crystalcomposition according to claim 18, wherein the ratio of the fifthcomponent is in the range of approximately 5% to approximately 30% byweight based on the total weight of the liquid crystal composition. 22.The liquid crystal composition according to claim 1, wherein the maximumtemperature of a nematic phase is approximately 70° C. or higher, theoptical anisotropy (25° C.) at a wavelength of 589 nanometers isapproximately 0.08 or more, and the dielectric anisotropy (25° C.) at afrequency of 1 kHz is approximately −2 or less.
 23. A liquid crystaldisplay device containing the liquid crystal composition according toclaim
 1. 24. The liquid crystal display device according to item 23,wherein an operating mode of the liquid crystal display device is a VAmode, an IPS mode or a PSA mode, and a driving mode of the liquidcrystal display device is an active matrix mode.